Hydraulic valve tappet



Nov. 23, 1954 G. T. RANDOL. 2,695,013

HYDRAULIC VALVE TAPPET Filed July a, 1955 n members thereof, aridI eirective 'to cetpensatef fo United States Patent 2,695,013 'HYnnULtcivLvn carrer Glenn'nnsndl, Mnntinrke'rsrkmd. -Applnanon fJuly'1s,-19ssl,f `sani No. 666,681 2s claims. s (onus-90) between the rocker armfof a drive train and thestemof the valve. As the engine is operated, the clearance'is increased due to impact and wear -of .the engagingparts. Increased clearancey betweenrthe rockeri'armsf'and valve stems results in i'neicient #and -oi'sy "operation of the engine and requires apartialdisassembly of the engine to adjust the tappets; that is, vto temporarily Correct the clearance between the rocker arms and valve stems byeiecting a manual adjustment in the ldrive train.

To avoid `the necessity of :frequent tappet adjustment and to eliminate `noisy and inecient loperation{f'pthe engine, some commercial"v engines yarev equipped'w-ith'hydraulic valve iifters which attempt to feiect automatic adjustment of the'valve drive train to maintain yzeroclearance in the train, so that in effect, the train functionsas a solid body in opening the valves `in the engine.

The general vobject of the present invention is to provide an improved valve 4lifter imechanism for tappet capable fof constantly and consistently maintainingsubstantiallyvzro clearance thereby eliminating backlash in the -valve drive train of an internal-combustionengine. 4

The primary object Vof 'the Ainventionis to provide for incorporation" in the Avalvedrivetra-infof a conventional internal-combu`stion engine, an 'improved 'automatically adjustable valve tappet of the hydraulically-operated type.

Another object of the inventionis toy provide an Aimproved hydraulic valve 'tappetparticularly adaptedfor-use with aConventional*valve'bperating cam, whichF-tppet provides for maintaining silencel'offperationand atords long life for the camitself `and the mechanism yoperated thereby.

Still another vobject of the linvention 'is to provideran `improved hydraulic f valvetappet l l'assembly that Vmay 'be readily substituted for any and =all=valve`liter 'n'echanisrns presently used commercially, whether mechanical o'rhydraulic. j

Itis a further object Aof ythe inventiontohfacilitate' the attainment of the recitedp'rimary"objective'byftheprovision of novel hydraulic tappet 11riecl1"a.n`isrno'f-heCompensating type which automaticallyadjustsfto'sltorte or lengthen the valve `drivetrain i-t'ona'intain r1es`tablish substantially zero clearancetherein, so that Whenladt'uated by a-cam, on thel'engine camshafLJ-is adapted 'tointerniittentlyl effect the 'cyclic open'iii'g 'andi closing ofFa-feorivehtional engine poppetvalve siler'ttl Fandfeii ly all operatin'g'speedsaid'ftlieiiia c'o d' A- still furth'erfobje'ctif he improved hydratilicvlv engagement :irrespective er inea-lautet relative i movement between ""tlei'iembers" *ofi the lifterftra'in.H l j As imperantes-je fgfhep municatioh i to theV tluid.. pressure chamber "said valve meanseomprisln'g a movable `substantially .engine `valve closed position the vpressure chamber.

.-poisi'tion, thelp'resent invention -slides 'on aV stem of the tappet, element spring biased in one direction to closed position and heldthere by increase in Huid pressure in said chamber and by the action f aninertia hammer or weight in its upward throw,

v'said weightbeing opposedzbya snubber spring carriedby 'said valve element'to ktransmit the weight force to said 4ielernentto assist in holding. the same closed, and to accelerate the downward movement-ofsaid weight into impact with:- thelvalve element to open the same upon the engine valve becoming closednotwithstanding the then existent pressure differentials across opposite sides of the valve "element-tend-to oppose'such valve opening action 'of the inertia hammer.

,Anfobject related tothe Object immediately above, is

to-incorporate in said ktap'pet mechanism novel and improved valve means controlled by a weight or inertia hammer vin such manner that the mot-ion of the tappet assembly operates to throw the Weight, on the opening cycle of the engine valve, in a/direction to supplement a spring anda modulated pressure of uid trappedbetween the tappet body members by the closing of. said valve, to

.''rrnlysseatl thevalve vvhile the engine camy is opening the engine valve; while upon the tappet assembly reaching weight is frnoved`downwardly into impact relation with the valve 'to open the-same to venable the engine valve mechanism to adjust according tothe backlash condition which may eXist,"said spring acting` to restore the valve and inertia mechanism to lightly seated relationshipwith respect to vI the port controlling iluid communication into the pressure chamber ofzthetappet assembly;the tappet unit engaging the base circle ofthe engine cam during the -spring restora- Ytive'` action whereby. lluid communication is provided into .the-:pressure .chamber 'ofthe tappet unit in Ireadiness for )another 'engine valve opening cycle.

lt is the 'objectief another embodiment of the invention 4tooprovide tappet mechanism in which the opening only Aof rthe check valve -is assisted bythe operation of an inertia sleeve Sliding on a fixed `stem and cooperating with a vspring for increasing its 'position vwhereby the check kvalve is positively apertured velocity toward valve opening at the proper time Vinthe engine valve cycle for the tappet to compensate for backlash and changes due to wear or thermal conditions in 'the valve train.

11n accomplishing the objects of the .present invention, I provide-a valve tappet mechanism having some similarity to commercial hydraulic valve litters and` 'including sub- Vstantiallyall `of the elements 'of commercial hydraulic ivalve lifters.

In lparticular, the'v-alve tappet mechanism ofthe present 'mvention comprises a pair of relatively movable body-members dening `a ud pressure chamber therebetween, passage means, including aport in one body' member, for'conducting uid under pressure to and fromv the chamber, and a checlevalve positioned within the chamber and adapted to lclose the port to close the The fluid inthe chamber is substantially incompressible and as a The body members are,

effect, locked together for conjoint movement to open the :engine valve. While somey reliance is placed upon t-he hydraulic impact principle, supplemented by spring action 'in certain types, as utilized in commercial hydraulic valve' litters to seat and hold the check-valve in closed v n provides improved additional mechanism operable by inertia force produced by aweight associated with said check-valve and in the nature fcushi'ofnthesleeve in 'flvalve closing movement and t0 assist `1t1in movement to` valv'e opening position. In anotherembodment the stem is jfxed to the part of the 'o'iilyjto openthe check-valve.

Other and yfurther objects and features of the present valve drive train,

' outer cylindrical invention will become more apparent to those skilled in ing and following specification wherein are disclosed two embodiments of the invention with the understanding that such changes may be made therein as fall within the scope of the appended claims without departing from the spirit of the invention.

In said drawings:

Figure l is a fragmentary transverse vertical section through a V-type internal-combustion.engine showing the overhead valve operating mechanism incorporating selfadjusting hydraulic valve tappets constructed in accordance with the present invention;

Figure 2 is an enlarged longitudinal central section through a tappet in the reposed or engine valve closed position;

Figure 3 is a view similar to that of Figure 2 but showing the tappet in engine valve open position;

Figure 4 is a View. similar to Figures 2 and 3 but showing .the tappet at the termination of an engine valve closing;

Figure 5 is a fragmentaryvview similar to Figure 2. but on a still larger scale and illustrating the inertia weight, its spring and the check-valve;

Figure 6 is a fragmentary horizontal section taken on line 6 6 of Figure 5; and

Figure 7 is a view similar to Figure 5 but illustrating a further embodiment.

Referring now to` the drawings, and particularly to Figure l, the invention is shown incorporated in a con ventional internal-combustion engine 10 having a plurality of poppet valves one of which is shown at 11. A indicated generally at 12, is provided for each valve of the engine, and is conventional in all respects except for the valve tappet mechanism of the present invention, which is embodied therein. The valve drive train 12 extends between the valve 11 and the cam shaft 14 of the engine. known construction and cludes a stem portion 16, guided in a collar part 17, and having spring means 18 associated therewith normally tending to close the valve. A rocker arm 19 pivotally mounted intermediate its ends on a suitable rock shaft 20 is adapted to bear at one end 21 thereof against the free end of stem 16 when rotated in a counterclockwise direction, as viewed in the figure, to open valve 11 against the force of spring means 18. The other end 22 of the rocker arm 19 has a hemispherical recess, not shown, in

its under surface to accommodate the outer end of a push l rod 24, the other ends of which bears against a dished fitting in the upper hollow end of a valve tappet 13, which will be later described.

The valve tappet, which is generally cylindrical in contour, is illustrated as slidably mounted in a bore 25 radially disposed, in respect to the axis of the cam shaft 14, in the block of the engine 10 so that the inner end of the tappet 13 bears on the surface of the cam allotted thereto.

The valve 11 may be of any that selected for illustration inthe art upon a consideration of the accompanying draw Referring now to Figure 2 for a more complete undei-, V

standing of the construction and functioning of the valve tappet 13, it will be seen that each of these comprises an outer shell or sleeve 26 having a working it in the bore 25 in the block of the engine, and having a closed bottom 27 which is adapted to bear on the surface of the cam as seen in the figure. The second principal element of the tappet comprises the plunger 28 of cup-like form, the

surface thereof sliding with a substantially oil-tight fit in the bore 29 in the shell part. The plunger is circular form having a projecting spout 31 extending downwardly below the bottom wall 32 of the plunger. A space or chamber 34 is seen to be confined between the walls of the smaller bore 35 at the lower portion of the tappet shell and the lower end of the plunger, which chamber when appropriately filled with oil and closed by a valve member over the port 30 functions as a solid element to cause lift of the valve train by the cam acting on the bottom of the shell. The plunger supports with a snap iit the push rod cup 37 fitting within its bore and.

having a ange overlying the plunger end. The dished upper surface of the cup provides accommodation for the ball end 39 of push rod 24. For convenience in construction the part engaging the ball end 39 is a conical taper as shown at 40. This provides for a line contact between the end of the push rod and the upper face of the cup closed at the bottom except for a port 30 of 'enabling it to slide loosely which serves more or less to seal against the outow of oilinan-upward-direction:- v-

There is thus formed a more or less tight reservoir 41 beneath the thimble 37 and above the bottom 32 of the plunger 28. This is constantly supplied with an excess quantity of oil from the pressure lubricating system of the engine, the pump of the system providing oil through a suitable conduit to the channel 42 in the wall of bore 25 in the engine block. This is in continuous communication with the circumferential groove 43 in the outer wall of the tappet shell which connects in turn to an inner channel 44 by way of radial bore 45. The cylindrical outer surface of the plunger is circumferentially grooved at 46 to provide a passage for oil which communicates through bore 47 with the reservoir 41 in the plunger.

A thin, fiat circular valve disc 50 serves to close the port 30 in the bottom of the plunger, acting at all times under the urge of a light helical spring 51 bearing on its lower surface and itself abutting against the bottom wall 52 of valve cage 53. The normal pretensioned status of the spring 51 is suicient to hold the valve disc 50 in its upper closed position (Figure 2) and counterbalance the static weight of novel inertia mechanism operably associated therewith which is to be described later, when the fluid pressure forces on opposite sides of the valve disc are equal; but the valve disc is readily moved downwardly against said spring action upon the pressure forces of the liquid in the passage 30 slightly exceeding those of the liquid below the disc valve in the chamber 34. The said cage is in the nature of a cup having its open upper end equipped with a radial ange to provide a wide base seating at 54 against the ilat bottom of the tappet plunger surrounding the bead on neck 31 against which it may have a snap fit if desired by appropriate inturned tongue construction. The inner diameter of the upper portion ofthe valve disc retainer provides a free clearance for the valve disc while the lower portion is reduced in diameter to form a seat to maintain the helical expansion spring 51 centralized in respect to the valve disc. This combined disc retainer and spring abutment is provided with a relatively large central aperture 56 to accommodate the free ilow of oil therethrough in its movement from reservoir 41 via passage 30 to chamber 34 and vice The plunger 28 is constantly biased outwardly tending to enlargechamber 34, by helical spring 57 the upper end of which bears on the shoulder at the junction of the two diameters of the valve disc retainer cup and the lower end of which fits in the small diameter bore at the lower end of the tappet body. This bore and the small diameter portion of the. valve disc retainer cup centralize this helical spring 57. To prevent separation of the two parts of the valve tappet when itis not incorporated in an engine, a suitable snap ring 58 tits in an appropriate internal groove near the upper end of the bore of the tappet shell and limits outward movement of the plunger cup.

' Referring now to Figure 5 for an enlarged view of the parts directly associated with the valve disc 50, it will be noted that against the upper side of this disc and centrally thereof is secured the stem 60 extending normally therefrom and having a loose sliding it in the central bore 61 in the lower part of the push rod cup 37. Since there is a possibility of a uid tight fit of the ball end 39 of the push rod in the upper surface of this cup, which might make the end of stem 60 act as a piston or plunger and retard its movement, relief bores 62 extending from near the top of the hole 61 through the lower surface of the push rod cup are provided as seen in this figure.

Fixed on the stem 60 at a suitable distance beneath the lower end of cup 37 is an abutment washer 63 against which the upper end of a conical spring 64 abuts as shown. The lower end of the spring is received in a cup washer 65 having a central bore slidably fitted over stem 60. To provide for a free ow of oil so that none may be trapped when the spring is being compressed, the bottom of cup washer 65 is provided with a circular series of holes 66 extending through it between the central stem and the last turn of the spring. This cup washer 65 bears lightly under the pressure of the spring against the top surface of an inertia weight or sleeve 68 having a central bore 69 on the stem 60. The upper and lower ends of this tubular weight are chamfered as at 69 and 70 t o facilitate its high speed movement through the mass of oil surrounding it. Obviously the weight may move relative to the stem 60 from its own inertia and vblock of the engine is `tappet in the manner labout to be rapid lYemei-ltof the valve tappet', 'causihg compressionof the spring as the sleeve moves upward relatively 'tl'.qereta `rWhen the forceskare in theopp'osite" direction the weight is moved downwardly toward the valve disc with increased` speed over that resulting `fromfinertia and Stem movement, theadditional energy being supplied by theexpanding action of 'the buffer spring 64. When the ,weight strikes the` upper surface` of the disc 50 it drives thelatter, away from its seat, releasing the modulated pressure in .the compartment 34 beneath it for purposes to be later. described. .l

In the modication of Figure 7, the, general arrangement Vof parts is identical with that already described in connection with Figures 2 and 5,y and similar reference `charactershave beenrappliedlt'o corresponding parts. In

,this case theI valve disc 50, `tive attachment to a stem'. the action of spring 51'.

embodiment is secured to is in. this case tightly fitted in bore 61 in the lower end of push rod cup 37', preferably by a press fit. This stem or 'guide rod stops just short of the plane of the face of ,thevalve seat and is formed to two diameters, the largest part 7S accommodating the bore in the inertia weight 68 to however, is free of any opera It isheld closed solely under The 'stem which in the earlier provide it with a sliding lit. The upper portion 77 of" 'the stem is reduced in diameter to provide a shoulder 76 on which rests a cup washer 78 perforated to slide freely Aoverportion 77. It serves to support the lower end of tapered spring 79, the upper end of which abuts the lower vface ofthe push rod cup 37. The spring may be under soi'ne initial tension or may be relaxed in accordance with design factors, the cup stopping against the shoulder 76, lservingto provide for anyr desired compression thereof.

In the construction shown in Figure 7 the inertia weight 6,3 `when resting on the seated valve disc 50 clears the under surface of the movable cup washer by a small amount in order that itv may achieve a certain degree of vupward movementv before coming "up against this washer and starting to compress the buicr spring. Likewise this precludes any o f the energy from spring79. being imparted through the weight continuously against the valve with a tendency to bias it toward open position such as might happen if all the adjustments were not accurately made at, thettime of initial assembly. In contrast with the noperation of the first described embodiment, which u'sfes the weight of both to assist in holding the valve closed yon its seat and in opening it under certain circumstances, this latter embodiment as shown in Figure 7 makes use f the inertia weight solely for vmoving the valve disc 50 off lof its seat at the time when the valve tappet is riding on the base circle of the cam. i

The construction of the devices under both embodiments of the invention is such as to provide a continual but slow llow and change of oil within the valve tappets. The sliding tit of the tappet body in the bore in the such that a certain small leakage takes place to maintain lubrication. The sliding t between the plunger and bore in the tappet body likewise provides a slight leak-by loss of oil. The engagement between thelower Vballend of the push rod andthe tapered upper ,surface of the push rod cup is such that there may beA a slight leakage here suiicient at lea'stmto maintain lubrication, the-oil escaping into the cup from reservoir 41 through the vent holes 62.y The operation'of the described `facilitates a slow but constant change of oilyin the closed cavity 34 between the plunger and the tappet body since the lcheckvalve `is opened lonce per cycle of the valve linkage and `at each time lets in and out a small 'quantity of the trapped oil. t

`The operation vof the valve lifter mechanism 13 of the rsteinbodiment of the invention is as follows: i,

With 'the engine valve in 'closed position 'the various e ments fof the mechanism assume the relative `positions illustrated inV Figures l and 2. Here the helical ,spri'n`g`f57 `between the tappet body 26 and plunger 28 exp'ainds` the tappet in length between the push rod 24 and the base circle` of the cam or shaft 14 so: that the lower Qend "2'7` of the tappet beas thereon with substantially the force exerted by spring 57. rlfhe entire assembly lis charged with oil from the lubricating system of the engine, as previously explained, any air initially trapped in the ,chamber 434 being slowly vented lthrough leakage between of the tappet body and being 85 the'plunger and the bore slowly replaced by oil during operation. Thestrngth the upper face of the valve disc 2O of spring 51 is barely enough t'o` maintain the valvedi's'c 50 against its seat.v i,

As'canr14'rta`tesina clockwise directionas viewed in the figures, the opening ramp 80 thereon which merges the base circle with the lift,` operatively engages the under end face of the tappet body and begins to lift the same either with a quick lift, if the cam is designed for the conventional type of hydraulic valve tappet, or with a slower more gentle lift if the cam is especially designed for tappets of the type of thepresent invention. Under these circumstances themovement of the tappet being resisted by the engine valve spring 18 through the push rod 24, tends to compress the solid ymass of oil in the compartment 34 between the tappet body and plunger which imparts a pressure or 'hydraulic impact to the under'surface of the vave disc which is already lightly seated and forces it tightly closed, thereby imprisoning the liquid within the compartment 34 in a suiciently solid acting mass to cause the parts of the valve tappet to move in unison and lift the engine valve as if a solid tappet were in place. The engine valve train clearance having been substantially zero at the position vindicated in Figure 2 because of the action of expanding spring 57 between the two tappet body parts, the action in operating the valve drive train is that of a mechanical lifter with substantially zerolash present. Y

When the cam valve opening ramp first strikes the under face of the tappet all parts associated therewith are given a rapid upward thrust including the inertia weight 68 solidly seated in the tightly closed valve disc which may also be slightly flexed by the hydraulic impact. Being unrestrained in its movement except by the light spring 64, the sleeve moves more rapidly than the other parts of the tappet under the initial impetus and compresses the spring 64 so that the weight moves up to the position illustrated in Figure 3 wherein its lower face is seen to be spaced well away from the valve disc 50. This condition holds at least until the cam reaches its position of maximum lift as illustrated in Figure 3 and all the time the weight is compressing spring 64 the latter reacts through its abutment 63 on the stem 60 to assist the helical spring 51 and the fluid pressure in the compartment 34 to hold the valve tightly against its seat under any tendency, such as might come from vibration or the like, to unseat it, thus insuring operation for this part of the cycle with substantially zero backlash and absolutely quiet operation of the valve train.

As the cam progresses from the maximum lift point Si to the release or valve closing ramp 82 the tappet is lowered and ,with it the engine valve is closed by action of spring 18., Under these `circumstances the downward movement of the tappet leaves the inertia weight lifted in the Figure 3 position continually imparting lift to the stem and the valve disc whereby to maintain it tightly onV its seat until the valve tappet rides olf of the ramp at 32. Here conditions reverse themselves, the downward movement of the tappet ceases, the inertia of the weight no longer is sufcient to overcome the expanding action of its spri g 64 and the weight, both under the action of gravity and the pressure of the spring, moves rapidly downwardly, striking the upper face of the valve disc Sil and thus driving it from its seat as shown in. Figures 4, in spite of the still considerable fluid pressure which may be behind it, thereby re-establishing 'iiuid communication between compartment 34 and oil reservoir 4l whereby an appropriate movement of oil in the required direction takes place. The springs '5l 6ft, are so weighted that at periods of rest the former predominates to 'lightly close the valve 50 but can be readily overcome by augmentation of the effect spring 54 responsive to the action 'of the inertia weight 'if there has been over compensation to reduce the clearance to less than 'zero (excess pressure on the base circle) then a certain amount of the oil 'may transfer back into reservoir 'Li-l', Yor if as lthe result of temperature changes `or wear in the valve train, there has been an accumulated backlash this is immediately taken up under the action `of spring 57 forcing the tappet to elongate and again reducing the vclearance to substantially zero. The slight tendency of the valve disc 50 toopen resulting from its ownl momentum is very 'materially augmented bythe action ofthe Vhamr'ner blow ofthe inertia weight moving under 'the impetus of its spring and thus cornplete opening of the valveis assured under all circum- 7 stances so that full compensation may be made for proper clearance adiustment.

'lhe valve disc e0 is held open under the conditions shown in rigure 4 during a substantial degree of arc during which the tappet body is riding on the base circle ot' the cam, but me momentum exect of the hammer weight is lost prior to approaching the opening ramp 8U so that the valve disc has lightly closed under the action ot' its spring 5l in readiness for the hydraulic impact when the tappet is lifted on this ramp to open the engine valve 11.

With the functioning of the first embodiment of the invention, it is clear that maximum eiiiciency of the hydraulic valve tappet is assured under all circumstances and that substantially zero-lash is achieved in the valve train during the whole time that the engine valve is opening and closing. After the engine valve closing and when the tappet valve disc 50 is open there is some slight relief of pressure on the heel or base circle of the cam so that minimum wear results on the contacting parts. With the tappet valve opening and closing once per cycle careful modulation and adiustment of the whole valve train is achieved that many times, so that the backlash or clearance in the whole train is maintained as near zero as is feasible and desirable, all with the addition of only a few very small and low priced parts to what has been considered as the normal or commercial type of hydraulic valve tappet.

ln the embodiment of the invention illustrated in Figure 7 obviously the weight has no effect in serving to close and hold shut the valve disc 50 since it is wholly independent thereof, as is the stem 75. Spring 51 is of such weight as to counterbalance the hammer 68 and the valve 5u so that the latter is lightly seated in closed position, as shown in the figure. When the weight is actuated by inertia it is cushioned in its upward movement during the engine valve opening cycle by the spring 79 which spring then adds to its acceleration on its downward movement to insure opening of the valve disc 50. Note that in this arrangement the upper end of the spring 'i9 is fixed whereas in the first embodiment the upper abutment for corresponding spring 64 moves with the valve disc, Thus the effectiveness of the spring 79 in Figure 7 is much greater and the hammer blow imparted to the valve disc under the action of its own and the momentum given it by this spring is such as to insure opening the valve disc in spite of a relatively high pressure of fluid within the chamber 34 beneath it.

ln both embodiments there is some bias of the valve 50 toward open position when the fluid pressure resulting from the engine oil circulating pump continually driving oil into the reservoir 41 under the not inconsiderable pressure resulting from the engine speed, slightly exceeds fluid pressures in the chamber 34. This pressure, of course, is relatively inconsequential compared with that built up in chamber 34 under the lift action of the cam and the resistance of the engine valve spring 18, but it is quite effective when the engine valve is seated to assist in lifting the disc 50 from its seat when uid pressure differences occur on opposite sides of the valve disc 50 whereby fluid communication is established via passage 30 between the reservoir 41 and chamber 34 enabling relative adjustments between the tappet body members 26, 28 as desired.

In Figure 7 the spring 51 is so rated as to substantially prevent the valve disc 50 from seating during the valve tappet engagement with the base circle of the engine cam, thus accommodating the lifter adjustment as required; i. e., shortening or lengthening the valve actuating linkage as required.

It will be noted that two elements operate to eliminate any backlash in the valve train, and both function during the time that the tappet is riding on the base circle of the cam. The rst of these is the expansion spring 57 tending to separate the two body parts or actually to elongate the tappet, and the second is the pressure of the oil from the engine circulating system endeavoring to enter the compartment 34 after lifting the check-valve from its seat.

The present invention is particularly adapted to be utilized in the replacement of all valve tappet mechaiiisms whether mechanical or hydraulic. While it is preferred that the cam design be conventional, as shown in the drawing, it is clear that the present invention will operate satisfactorily with the particular cam design 8 presently used for commercial hydraulic valve tappets where the ramp gives a rapid rise to the tappet in order to provide the hydraulic impact to insure the closing of the tappet valve substantially at the instant of initial tappet lift.

it will be apparent that various changes, modifications and rearrangements can be made in the particular apparatus described herein without departing from the scope of my invention. Obviously one body member of the tappet need not be arranged within the other and the various parts and elements of the construction may be redesigned to fit particular installations or designs, and obvious substitutes may be used for the various parts shown.

l claim as my invention:

l. A hydraulic valve tappet comprising a pair of relatively movable members delining a chamber therebetween, a source of liquid, a spring for biasing said pair of members apart, a valve port in one of said members establishing communication between said source of liquid and said chamber, a check-valve adapted to close said port against pressure in the chamber, a spring for biasing said check-valve to close said port, and inertia means operatively associated with said valve, said means being adapted for actuation in response to tappet movement for supplementing said last named spring to hold said valve agalinst said port during the lift portion of the tappet cyc e.

2. The valve tappet of claim 1 in which said inertia means comprisises a weight and means providing a lostinotion connection between said weight and valve whereby the weight assists the spring to close the valve during engine valve open phases of the cycle and the weight opposes the spring to open the valve during valve closed phases of the cycle.

3. The valve tappet of claim 2 in which a buffer spring resists movement of the weight toward valve closing action and in which the buler spring imparts momentum to the weight toward valve opening position.

4. A hydraulic valve tappet comprising a pair of relatively movable members dening a chamber therebetween, a source of liquid, a valve port in one of said members establishing communication between said source of liquid and said chamber, a check-valve adapted to close said port against pressure in the chamber, a spring for biasing said check-valve to close said port, an expansion spring biasing said pair of members apart, inertia means comprising a weight slidable longitudinally of the tappet in respect to the ported member, and means guiding the weight to strike the check-valve to open the same against its biasing spring when tappet motion stops after downward movement.

5. The tappet of claim 4 in which spring means are positioned to be compressed by said weight during upward movement of the tappet.

6. The tappet of claim 5 in which said spring means is operably interposed between an abutment immovable on the said ported member and a movable seat normally engaging a shoulder formed on said guiding means in spaced relation with respect to said check-valve.

7. The tappet of claim 6 in which the spring seat when engaging said shoulder provides a predetermined lostrnotion movement of the Weight between said spring means and the check valve.

8. The tappet of claim 7 in which said spring means comprises a conical spiral spring surrounding said guiding means on which the weight is slidable.

9. A hydraulic valve tappet comprising a cup-like body portion adapted for cam actuated reciprocation in a motor block, a cup-like plunger reciprocably nested in said body portion to define a chamber therebetween, an expansion spring in said chamber tending to enlarge it, a push rod cup nesting in said plunger to form a reservoir therein adapted to be connected to a source of liquid, a port in the bottom of said plunger connecting the chamber and reservoir, a check-valve disc cooperating with said port and located in the chamber, a spring biasing said disc to close the port, an inertia weight adapted to bear on said disc when the tappet is at rest and means in said reservoir guiding said weight for reciprocation on the axis of movement of the tappet.

10. The tappet of claim 9 in which the weight is a sleeve and the guide means is a rod entering a hole in said push rod cup.

Il. The tappet of claim l in which the ends of the weight are tapered to facilitate its movement through said li uid.

Q12. The tappet of claim 9 in which a butler spring is mounted on said rod and a top abutment for said spring whereby it is compressed when inertia causes a relative movement of the weight against it.

13. The tappet of claim 12 in which the said rod is rigidly attached to said disc and slides in said hole in the push rod cup.

14. The tappet of claim 13 in which the spring abutment is secured to the rod and the spring normally engages the weight with a light pressure.

15. The tappet of claim il) in which the rod is rigidly secured to the valve disc and has a sliding lit in said push rod cup hole.

16. The tappet of claim in which the rod is rigidly secured in the hole in the push rod cup and the free end thereof is spaced from the disc.

17. The tappet of claim 16 in which a spring is mounted on said rod, an abutment for the upper end of said spring, the lower end of the spring being free or engagement with the said weight.

18. The tappet of claim 17 in which the spring is preloaded by a washer forming its lower abutment, having a sliding tit on the rod and normally biased against a shoulder thereon.

19. The tappet of claim 18 in conical coil spring.

20. The tappet of claim 14 in which the spring is a conical coil spring.

21. In a hydraulic compensating valve tappet for in* ternal-combustion engines including a camactuated tappet body having a longitudinal cylindrical bore closed at one end and open at the other, a hollow plunger reciprocable in said bore and providing a liquid reservoir, a source of liquid, spring means for axially elongating said tappet body and plunger assembly relatively to each other, a liquid chamber formed between the closed end of said tappet body and the inner end of said plunger, a Valve port in the inner end of said plunger forming a Valve seat for interconnecting said liquid reservoir and cham- Which the spring is a ber, an inwardly opening valve element engageable with said valve seat to close the Valve port, spring means for biasing said valve element into engagement with said valve seat to close said valve port, and inertia means operably associated with said valve element responsive to tappet body movement for supplementing the biasing action of said last-named spring means to maintain said valve port closed during a lift portion of the tappet cycle.

22. The hydraulic compensating tappet according to claim 2l in which said inertia means include a movable element responsive to tappet motion, and spring means operably associated therewith and operatively energized thereby during the lift portion of the tappet cycle for accelerating the downward motion of said movable element into impact with said valve element to open the same substantially at the arrested point of tappet motion.

23. The hydraulic compensating tappet according to claim 22 in which the inertia means includes means limiting the effectiveness of said last-named spring means on said movable element to accelerate the same as aforesaid.

24. The hydraulic compensating tappet according to claim 22 in which the second-named spring means is elf-estive to counterbalance the third-named spring means and the static weight of said movable element at substantially closed position of said valve element.

25. The hydraulic compensating tappet according to claim 23 in which the second-named spring means is effective to counterbalance the static weight only of the said inertia movable element at substantially closed position or" said valve element.

References Cited in the le oi this patent UNITED STATES PATENTS Number Name Date 2,5l6,l72 Baldwin July 25, 1950 2,599,886 Bergmann d .lune 10, 1952 FOREIGN PATENTS Number Country Date 584,302 Great Britain Jan. l0, 1947 

